The present disclosure relates to an exhaust gas recirculating apparatus for an internal combustion engine.
An internal combustion engine has an intake manifold that has intake passages. The intake passages are aligned in the direction in which cylinders are aligned and connected to the respective cylinders. The intake manifold may have an exhaust gas recirculating apparatus to introduce exhaust gas into the respective intake passages.
The exhaust gas recirculating apparatus described in Japanese Laid-Open Patent Publication No. 2005-226585 has an exhaust gas distributing portion and introduction passages. The exhaust gas distributing portion distributes exhaust gas to two adjacent intake passages. The introduction passages introduce the exhaust gas from the exhaust gas distributing portion to the corresponding intake passages. The two intake passages are located on the opposite sides of the exhaust gas distributing portion. The introduction passages are arranged on the side surfaces of the corresponding intake passages. In this configuration, the exhaust gas supplied to the exhaust gas distributing portion is introduced into the two intake passages via the corresponding introduction passages. Also known is an exhaust gas recirculating apparatus, as described in Japanese Laid-Open Patent Publication No. 2000-192859, in which an introduction passage is arranged in the middle of an intake passage.
In some cases, due to intake pulsations in the intake passages or delayed closure of the intake valves, the fresh air that has been drawn into a cylinder may blow back from the intake passage to one of the introduction passages, which communicates with the exhaust gas distributing portion. After blowing back from the intake passage, the fresh air flows into an adjacent intake passage via the other introduction passage, which communicates with the exhaust gas distributing portion. As a result, the fresh air decreases the introduction amount of exhaust gas in the adjacent intake passage. This varies the introduced amount of exhaust gas among the cylinders.